EX10-20

REGISTRATION RIGHTS AGREEMENT

Registration Rights Agreement (the "Agreement"), dated as of June 28, 2004, by
and between Human BioSystems, a corporation organized under the laws of State of
California, with its principal executive office at with its principal executive
office at 1127 Harker Avenue, Palo Alto, California, 94301, (the "Company"), and
Dutchess Private Equities Fund, II, L.P., a Delaware limited partnership with
its principal office at 312 Stuart Street, Boston, MA 02116 (the "Investor").

Whereas, in connection with the Investment Agreement by and between the Company
and the Investor of even date herewith (the "Investment Agreement"), the Company
has agreed to issue and sell to the Investor an indeterminate number of shares
of the Company's Common Stock, no par value per share (the "Common Stock"), to
be purchased pursuant to the terms and subject to the conditions set forth in
the Investment Agreement; and

Whereas, to induce the Investor to execute and deliver the Investment Agreement,
the Company has agreed to provide certain registration rights under the
Securities Act of 1933, as amended, and the rules and regulations thereunder, or
any similar successor statute (collectively, the "1933 Act"), and applicable
state securities laws, with respect to the shares of Common Stock issuable
pursuant to the Investment Agreement.

Now therefore, in consideration of the foregoing premises and the mutual
covenants contained hereinafter and other good and valuable consideration, the
receipt and sufficiency of which are hereby acknowledged, the Company and the
Investor hereby agree as follows:

Section 1.  DEFINITIONS.

As used in this Agreement, the following terms shall have the following
meanings:

"Execution Date" means the date first written above.

"Investor" means Dutchess Private Equities Fund, II, L.P., a Delaware limited
partnership.

"Person" means a corporation, a limited liability company, an association, a
partnership, an organization, a business, an individual, a governmental or
political subdivision thereof or a governmental agency.

"Principal Market" shall mean The American Stock Exchange, National Association
of Securities Dealer's, Inc. Over-the-Counter electronic bulletin board, the
Nasdaq National Market or The Nasdaq SmallCap Market whichever is the principal
market on which the Common Stock is listed.

"Register," "Registered," and "Registration" refer to a registration effected by
preparing and filing one or more Registration Statements in compliance with the
1933 Act and pursuant to Rule 415 under the 1933 Act or any successor rule
providing for offering securities on a continuous basis ("Rule 415"), and the
declaration or ordering of effectiveness of such Registration Statement(s) by
the United States Securities and Exchange Commission (the "SEC").

"Registrable Securities" means (i) the shares of Common Stock issued or issuable
pursuant to the Investment Agreement, and (ii) any shares of capital stock
issued or issuable with respect to such shares of Common Stock, if any, as a
result of any stock split, stock dividend, recapitalization, exchange or similar
event or otherwise, which have not been (x) included in a Registration Statement
that has been declared effective by the SEC or (y) sold under circumstances
meeting all of the applicable conditions of Rule 144 (or any similar provision
then in force) under the 1933 Act.

"Registration Statement" means a registration statement of the Company filed
under the 1933 Act covering the Registrable Securities.

All capitalized terms used in this Agreement and not otherwise defined herein
shall have the same meaning ascribed to them as in the Investment Agreement.

Section 2.  REGISTRATION.

(a)  On or before the execution of this Agreement, the Company shall have
provided a draft of the Registration Statement covering the Registrable
Securities to the Investor. The Company shall, as soon as practicable, but not
later than fifteen calendar days following the Execution Date, file with the SEC
a Registration Statement or Registration Statements (as is necessary) on Form
SB-2 (or, if such form is unavailable for such a registration, on such other
form as is available for such a registration), covering the resale of all of the
Registrable Securities, which Registration Statement(s) shall state that, in
accordance with Rule 416 promulgated under the 1933 Act, such Registration
Statement also covers such indeterminate number of additional shares of Common
Stock as may become issuable upon stock splits, stock dividends or similar
transactions.  The Company shall initially register for resale _________ shares
of Common Stock which would be issuable on the date preceding the filing of the
Registration Statement based on the closing bid price of the Company's Common
Stock on such date and the amount reasonably calculated that represents Common
Stock issuable to other parties as set forth in the Investment Agreement except
to the extent that the SEC requires the share amount to be reduced as a
condition of effectiveness..

(b)  The Company shall use commercially reasonable efforts to have the
Registration Statement(s) declared effective by the SEC within 90 calendar days
after the Execution Date.

(c)  The Company agrees not to include any other securities in the Registration
Statement covering the Registrable Securities without Investor's prior written
consent which Investor may withhold in its sole discretion. Furthermore, the
Company agrees that with the exception of a Form S-8 that may be filed to
register for resale shares of common stock issued to employees of the Company in
exchange for salaries, it will not file any other Registration Statement for
other securities, until thirty calendar days after the Registration Statement
for the Registrable Securities is declared effective by the SEC.

Section 3.  RELATED OBLIGATIONS.

 At such time as the Company is obligated to prepare and file a Registration
 Statement with the SEC pursuant to Section 2(a), the Company will effect the
 registration of the Registrable Securities in accordance with the intended
 method of disposition thereof and, with respect thereto, the Company shall have
 the following obligations:

(a)  The Company shall use commercially reasonable efforts to cause such
Registration Statement relating to the Registrable Securities to become
effective within 90 days after the Execution Date and shall keep such
Registration Statement effective until the earlier to occur of (i) the date as
of which the Investor may sell all of the Registrable Securities without
restriction pursuant to Rule 144(k) promulgated under the 1933 Act (or successor
thereto); or (ii) the date on which (A) the Investor shall have sold all the
Registrable Securities; and (B) the Investor has no right to acquire any
additional shares of Common Stock under the Investment Agreement (the
"Registration Period").  The Registration Statement (including any amendments or
supplements thereto and prospectuses contained therein) shall not contain any
untrue statement of a material fact or omit to state a material fact required to
be stated therein, or necessary to make the statements therein, in light of the
circumstances in which they were made, not misleading. The Company shall use its
best efforts to respond to all SEC comments within seven business days from
receipt of such comments by the Company. The Company shall use its best efforts
to cause the Registration Statement relating to the Registrable Securities to
become effective no later than three business days after notice from the SEC
that the Registration Statement may be declared effective.  The Investor agrees
to provide all information which it is required by law to provide to the
Company, including the intended method of disposition of the Registrable
Securities, and the Company's obligations set forth above shall be conditioned
on the receipt of such information.

(b)  The Company shall prepare and file with the SEC such amendments (including
post-effective amendments) and supplements to a Registration Statement and the
prospectus used in connection with such Registration Statement, which prospectus
is to be filed pursuant to Rule 424 promulgated under the 1933 Act, as may be
necessary to keep such Registration Statement effective during the Registration
Period, and, during such period, comply with the provisions of the 1933 Act with
respect to the disposition of all Registrable Securities of the Company covered
by such Registration Statement until such time as all of such Registrable
Securities shall have been disposed of in accordance with the intended methods
of disposition by the Investor thereof as set forth in such Registration
Statement.  In the event the number of shares of Common Stock covered by a
Registration Statement filed pursuant to this Agreement is at any time
insufficient to cover all of the Registrable Securities, the Company shall amend
such Registration Statement, or file a new Registration Statement (on the short
form available therefor, if applicable), so as to cover all of the Registrable
Securities, in each case, as soon as practicable, but in any event within 30
calendar days after the necessity therefor arises (based on the then Purchase
Price of the Common Stock and other relevant factors on which the Company
reasonably elects to rely), assuming the Company has sufficient authorized
shares at that time, and if it does not, within 30 calendar days after such
shares are authorized.  The Company shall use commercially reasonable efforts to
cause such amendment and/or new Registration Statement to become effective as
soon as practicable following the filing thereof.

(c)  The Company shall make available to the Investor whose Registrable
Securities are included in any Registration Statement and its legal counsel
without charge (i) promptly after the same is prepared and filed with the SEC at
least one copy of such Registration Statement and any amendment(s) thereto,
including financial statements and schedules, all documents incorporated therein
by reference and all exhibits, the prospectus included in such Registration
Statement (including each preliminary prospectus) and, with regards to such
Registration Statement(s), any correspondence by or on behalf of the Company to
the SEC or the staff of the SEC and any correspondence from the SEC or the staff
of the SEC to the Company or its representatives; (ii) upon the effectiveness of
any Registration Statement, the Company shall make available copies of the
prospectus included in such Registration Statement and all amendments and
supplements thereto; and (iii) such other documents, including copies of any
preliminary or final prospectus, as the Investor may reasonably request from
time to time in order to facilitate the disposition of the Registrable
Securities.

(d)  The Company shall use commercially reasonable efforts to (i) register and
qualify the Registrable Securities covered by a Registration Statement under
such other securities or "blue sky" laws of such states in the United States as
any Investor reasonably requests; (ii) prepare and file in those jurisdictions,
such amendments (including post-effective amendments) and supplements to such
registrations and qualifications as may be necessary to maintain the
effectiveness thereof during the Registration Period; (iii) take such other
actions as may be necessary to maintain such registrations and qualifications in
effect at all times during the Registration Period, and (iv) take all other
actions reasonably necessary or advisable to qualify the Registrable Securities
for sale in such jurisdictions; provided, however, that the Company shall not be
required in connection therewith or as a condition thereto to (x) qualify to do
business in any jurisdiction where it would not otherwise be required to qualify
but for this Section 3(d), or (y) subject itself to general taxation in any such
jurisdiction.  The Company shall promptly notify each Investor who holds
Registrable Securities of the receipt by the Company of any notification with
respect to the suspension of the registration or qualification of any of the
Registrable Securities for sale under the securities or "blue sky" laws of any
jurisdiction in the United States or its receipt of actual notice of the
initiation or threatening of any proceeding for such purpose.

(e)  As promptly as practicable after becoming aware of such event, the Company
shall notify each Investor in writing of the happening of any event as a result
of which the prospectus included in a Registration Statement, as then in effect,
includes an untrue statement of a material fact or omission to state a material
fact required to be stated therein or necessary to make the statements therein,
in light of the circumstances under which they were made, not misleading
("Registration Default") and use all diligent efforts to promptly prepare a
supplement or amendment to such Registration Statement and take any other
necessary steps to cure the Registration Default, (which, if such Registration
Statement is on Form S-3, may consist of a document to be filed by the Company
with the SEC pursuant to Section 13(a), 13(c), 14 or 15(d) of the 1934 Act (as
defined below) and to be incorporated by reference in the prospectus) to correct
such untrue statement or omission, and make available copies of such supplement
or amendment to each Investor. The Company shall also promptly notify each
Investor (i) when a prospectus or any prospectus supplement or post-effective
amendment has been filed, and when a Registration Statement or any post-
effective amendment has become effective (the Company will prepare notification
of such effectiveness which shall be delivered to the Investor on the same day
of such effectiveness and by overnight mail), additionally, the Company will
promptly provide to the Investor a copy of the effectiveness order prepared by
the SEC once it is received by the Company; (ii) of any request by the SEC for
amendments or supplements to a Registration Statement or related prospectus or
related information, (iii) of the Company's reasonable determination that a
post-effective amendment to a Registration Statement would be appropriate, (iv)
in the event the Registration Statement is no longer effective, or (v) if
Registration Statement is stale as a result of the Company's failure to timely
file its financials or otherwise.

(f)  The Company shall use commercially reasonable efforts to prevent the
issuance of any stop order or other  suspension of effectiveness of a
Registration Statement, or the suspension of the qualification of any of the
Registrable Securities for sale in any jurisdiction and, if such an order or
suspension is issued,  to obtain the withdrawal of such order or suspension at
the earliest possible moment and to notify the Investor who holds Registrable
Securities being sold of the issuance of such order and the  resolution thereof
or its receipt of actual notice of the initiation or threat of any proceeding
for such  purpose.

(g)  The Company shall permit the Investor and one legal counsel, designated by
the Investor, to review and comment upon a Registration Statement and all
amendments and supplements thereto at least three business days prior to their
filing with the SEC, and not file any document in a form to which such counsel
reasonably objects.  The Company may request to shorten the Investor's review
period and the Investor will, if possible, attempt to comply with the
accelerated review period.  The Company shall not submit to the SEC a request
for acceleration of the effectiveness of a Registration Statement or file with
the SEC a Registration Statement or any amendment or supplement thereto without
the prior approval of such counsel, which approval shall not be unreasonably
withheld.

(h)  At the request of the Investor, the Company shall cause to be furnished to
such Investor, on the date of the effectiveness of a Registration Statement, a
legal opinion, in form and substance reasonably acceptable to Investor's
counsel, dated as of such date, of counsel representing the Company for purposes
of such Registration Statement.

(i)  The Company shall make available for inspection by (i) the Investor and
(ii) one legal counsel and one firm of accountants or other agents retained by
the Investor (collectively, the "Inspectors"), all pertinent financial and other
records, and pertinent corporate documents and properties of the Company
(collectively, the "Records"), as shall be reasonably deemed necessary by each
Inspector, and cause the Company's officers, directors and employees to supply
all information which any Inspector may reasonably request; provided, however,
that each Inspector shall hold in strict confidence and shall not make any
disclosure (except to a Investor) or use of any Record or other information
which the Company determines in good faith to be confidential, and of which
determination the Inspectors are so notified, unless (a) the disclosure of such
Records is necessary to avoid or correct a misstatement or omission in any
Registration Statement or is otherwise required under the 1933 Act, (b) the
release of such Records is ordered pursuant to a final, non-appealable subpoena
or order from a court or government body of competent jurisdiction, or (c) the
information in such Records has been made generally available to the public
other than by disclosure in violation of this or any other agreement of which
the Inspector has knowledge.  Each Investor agrees that it shall, upon learning
that disclosure of such Records is sought in or by a court or governmental body
of competent jurisdiction or through other means, give prompt notice to the
Company and allow the Company, at its expense, to undertake appropriate action
to prevent disclosure of, or to obtain a protective order for, the Records
deemed confidential.

(j)  The Company shall hold in confidence and not make any disclosure of
information concerning a Investor provided to the Company unless (i) disclosure
of such information is necessary to comply with federal or state securities
laws, (ii) the disclosure of such information is necessary to avoid or correct a
misstatement or omission in any Registration Statement, (iii) the release of
such information is ordered pursuant to a subpoena or other final, non-
appealable order from a court or governmental body of competent jurisdiction, or
(iv) such information has been made generally available to the public other than
by disclosure in violation of this Agreement or any other agreement.  The
Company agrees that it shall, upon learning that disclosure of such information
concerning a Investor is sought in or by a court or governmental body of
competent jurisdiction or through other means, give prompt written notice to
such Investor and allow such Investor, at the Investor's expense, to undertake
appropriate action to prevent disclosure of, or to obtain a protective order
for, such information.

(k)  The Company shall use commercially reasonable efforts to maintain
designation and quotation of all the Registrable Securities covered by any
Registration Statement on the Principal Market.  If, despite the Company's best
efforts, the Company is unsuccessful in satisfying the preceding sentence, it
shall use commercially reasonable efforts to cause all the Registrable
Securities covered by any Registration Statement to be listed on each other
national securities exchange and automated quotation system, if any, on which
securities of the same class or series issued by the Company are then listed, if
any, if the listing of such Registrable Securities is then permitted under the
rules of such exchange or system.  The Company shall pay all fees and expenses
in connection with satisfying its obligation under this Section 3(k).

(l)  The Company shall cooperate with the Investor to facilitate the prompt
preparation and delivery of certificates (not bearing any restrictive legend)
representing the Registrable Securities to be offered pursuant to a Registration
Statement and enable such certificates to be in such denominations or amounts,
as the case may be, as the Investor may reasonably request.

(m)  The Company shall provide a transfer agent for all the Registrable
Securities not later than the effective date of the first Registration Statement
filed pursuant hereto.

(n)  If requested by the Investor, the Company shall (i) as soon as reasonably
practical incorporate in a prospectus supplement or post-effective amendment
such information as such Investor reasonably determines should be included
therein relating to the sale and distribution of Registrable Securities,
including, without limitation, information with respect to the offering of the
Registrable Securities to be sold in such offering; (ii) make all required
filings of such prospectus supplement or post-effective amendment as soon as
reasonably possible after being notified of the matters to be incorporated in
such prospectus supplement or post-effective amendment; and (iii) supplement or
make amendments to any Registration Statement if reasonably requested by such
Investor.

(o)  The Company shall use commercially reasonable efforts to cause the
Registrable Securities covered by the applicable Registration Statement to be
registered with or approved by such other governmental agencies or authorities
as may be necessary to consummate the disposition of such Registrable
Securities.

(p)  The Company shall otherwise use commercially reasonable efforts to comply
with all applicable rules and regulations of the SEC in connection with any
registration hereunder.

(q)  Within one business day after the Registration Statement which includes
Registrable Securities is declared effective by the SEC, the Company shall
deliver to the transfer agent for such Registrable Securities, with copies to
the Investor, confirmation that such Registration Statement has been declared
effective by the SEC.

(r)  The Company shall take all other reasonable actions necessary to expedite
and facilitate disposition by the Investor of Registrable Securities pursuant to
a Registration Statement.

Section 4.  OBLIGATIONS OF THE INVESTOR.

(a)  At least five calendar days prior to the first anticipated filing date of a
Registration Statement  the Company shall notify the Investor in writing of the
information the Company requires from each such Investor if such Investor elects
to have any of such Investor's Registrable Securities included in such
Registration Statement.  It shall be a condition precedent to the obligations of
the Company to complete the registration pursuant to this Agreement with respect
to the Registrable Securities of a particular Investor that such Investor shall
furnish in writing to the Company such information regarding itself, the
Registrable Securities held by it and the intended method of disposition of the
Registrable Securities held by it as shall reasonably be required to effect the
registration of such Registrable Securities and shall execute such documents in
connection with such registration as the Company may reasonably request.  Each
Investor covenants and agrees that, in connection with any sale of Registrable
Securities by it pursuant to a Registration Statement, it shall comply with the
"Plan of Distribution" section of the current prospectus relating to such
Registration Statement.

(b)  The Investor, by such Investor's acceptance of the Registrable Securities,
agrees to cooperate with the Company as reasonably requested by the Company in
connection with the preparation and filing of any Registration Statement
hereunder, unless such Investor has notified the Company in writing of such
Investor's election to exclude all of such Investor's Registrable Securities
from such Registration Statement.

(c)  The Investor agrees that, upon receipt of written notice from the Company
of the happening of any event of the kind described in Section 3(f) or the first
sentence of 3(e), such Investor will immediately discontinue disposition of
Registrable Securities pursuant to any Registration Statement(s) covering such
Registrable Securities until such Investor's receipt of the copies of the
supplemented or amended prospectus contemplated by Section 3(f) or the first
sentence of 3(e).

Section 5.  EXPENSES OF REGISTRATION.

All expenses, other than underwriting discounts and commissions and other than
as set forth in the Investment Agreement, incurred in connection with
registrations including comments, filings or qualifications pursuant to Sections
2 and 3, including, without limitation, all registration, listing and
qualifications fees, printing and accounting fees, and fees and disbursements of
counsel for the Company or for the Investor shall be paid by the Company.

Section 6.  INDEMNIFICATION.

In the event any Registrable Securities are included in a Registration Statement
under this Agreement:

(a)  To the fullest extent permitted by law, the Company will, and hereby does,
indemnify, hold harmless and defend each Investor who holds such Registrable
Securities, the directors, officers, partners, employees, counsel, agents,
representatives of, and each Person, if any, who controls, any Investor within
the meaning of the 1933 Act or the Securities Exchange Act of 1934, as amended
(the "1934 Act") (each, an "Indemnified Person"), against any losses, claims,
damages, liabilities, judgments, fines, penalties, charges, costs, attorneys'
fees, amounts paid in settlement or expenses, joint or several (collectively,
"Claims"), incurred in investigating, preparing or defending any action, claim,
suit, inquiry, proceeding, investigation or appeal taken from the foregoing by
or before any court or governmental, administrative or other regulatory agency,
body or the SEC, whether pending or threatened, whether or not an indemnified
party is or may be a party thereto ("Indemnified Damages"), to which any of them
may become subject insofar as such Claims (or actions or proceedings, whether
commenced or threatened, in respect thereof) arise out of or are based upon: (i)
any untrue statement or alleged untrue statement of a material fact in a
Registration Statement or any post-effective amendment thereto or in any filing
made in connection with the qualification of the offering under the securities
or other "blue sky" laws of any jurisdiction in which the Investor has requested
in writing that the Company register or qualify the Shares ("Blue Sky Filing"),
or the omission or alleged omission to state a material fact required to be
stated therein or necessary to make the statements therein, in light of the
circumstances under which the statements therein were made, not misleading, (ii)
any untrue statement or alleged untrue statement of a material fact contained in
the final prospectus (as amended or supplemented, if the Company files any
amendment thereof or supplement thereto with the SEC) or the omission or alleged
omission to state therein any material fact necessary to make the statements
made therein, in light of the circumstances under which the statements therein
were made, not misleading, or (iii) any violation or alleged violation by the
Company of the 1933 Act, the 1934 Act, any other law, including, without
limitation, any state securities law, or any rule or regulation thereunder
relating to the offer or sale of the Registrable Securities pursuant to a
Registration Statement (the matters in the foregoing clauses (i) through (iii)
being, collectively, "Violations").  Subject to the restrictions set forth in
Section 6(c) with respect to the number of legal counsel, the Company shall
reimburse the Investor and each such controlling person, promptly as such
expenses are incurred and are due and payable, for any reasonable legal fees or
other reasonable expenses incurred by them in connection with investigating or
defending any such Claim. Notwithstanding anything to the contrary contained
herein, the indemnification agreement contained in this Section 6(a): (i) shall
not apply to a Claim arising out of or based upon a Violation which is due to
the inclusion in the Registration Statement of the information furnished to the
Company by any Indemnified Person expressly for use in connection with the
preparation of the Registration Statement or any such amendment thereof or
supplement thereto; (ii) shall not be available to the extent such Claim is
based on (a) a failure of the Investor to deliver or to cause to be delivered
the prospectus made available by the Company or (b) the Indemnified Person's use
of an incorrect prospectus despite being promptly advised in advance by the
Company in writing not to use such incorrect prospectus;  (iii) any claims based
on the manner of sale of the Registrable Securities by the Investor or of the
Investor's failure to register as a dealer under applicable securities laws;
(iv) any omission of the Investor to notify the Company of any material fact
that should be stated in the Registration Statement or prospectus relating to
the Investor or the manner of sale; and (v) any amounts paid in settlement of
any Claim if such settlement is effected without the prior written consent of
the Company, which consent shall not be unreasonably withheld.  Such indemnity
shall remain in full force and effect regardless of any investigation made by or
on behalf of the Indemnified Person and  shall survive the resale of the
Registrable Securities by the Investor pursuant to the Registration Statement.

(b)  In connection with any Registration Statement in which a Investor is
participating, each such Investor agrees to severally and jointly indemnify,
hold harmless and defend, to the  same extent and in the same manner as is set
forth in Section 6(a), the Company, each of its  directors, officers, employees,
counsel, agents, representatives of, and each Person, if any, who controls the
Company within the meaning of the 1933 Act or the 1934 Act and the Company's
agents (collectively and together with an Indemnified Person, an "Indemnified
Party"), against any Claim or Indemnified Damages to which any of them may
become subject, under the 1933 Act, the 1934 Act or otherwise, insofar as such
Claim or Indemnified Damages arise out of or are based upon any Violation, in
each case to the extent, and only to the extent, that such Violation is due to
the inclusion in the Registration Statement of the written information furnished
to the Company by such Investor expressly for use in connection with such
Registration Statement; and, subject to Section 6(c), such Investor will
reimburse any legal or other expenses reasonably incurred by them in connection
with investigating or defending any such Claim; provided, however, that the
indemnity agreement contained in this Section 6(b) and the agreement with
respect to contribution contained in Section 7 shall not apply to amounts paid
in settlement of any Claim if such settlement is effected without the prior
written consent of such Investor, which consent shall not be unreasonably
withheld; provided, further, however, that the Investor shall be liable under
this Section 6(b) for only that amount of a Claim or Indemnified Damages as does
not exceed the net proceeds to such Investor as a result of the sale of
Registrable Securities pursuant to such Registration Statement.  Such indemnity
shall remain in full force and effect regardless of any investigation made by or
on behalf of such Indemnified Party and shall survive the resale of the
Registrable Securities by the Investor pursuant to the Registration Statement.
Notwithstanding anything to the contrary contained herein, the indemnification
agreement contained in this Section 6(b) with respect to any preliminary
prospectus shall not inure to the benefit of any Indemnified Party if the untrue
statement or omission of material fact contained in the preliminary prospectus
were corrected on a timely basis in the prospectus, as then amended or
supplemented.  This indemnification provision shall apply separately to each
Investor and liability hereunder shall not be joint and several.

(c)  Promptly after receipt by an Indemnified Person or Indemnified Party under
this Section 6 of notice of the commencement of any action or proceeding
(including any governmental action or proceeding) involving a Claim, such
Indemnified Person or Indemnified Party shall, if a Claim in respect thereof is
to be made against any indemnifying party under this Section 6, deliver to the
indemnifying party a written notice of the commencement thereof, and the
indemnifying party shall have the right to participate in, and, to the extent
the indemnifying party so desires, jointly with any other indemnifying party
similarly noticed, to assume control of the defense thereof with counsel
mutually satisfactory to the indemnifying party and the Indemnified Person or
the Indemnified Party, as the case may be; provided, however, that an
Indemnified Person or Indemnified Party shall have the right to retain its own
counsel with the fees and expenses to be paid by the indemnifying party, if, in
the reasonable opinion of counsel retained by the Indemnified Person or
Indemnified Party, the representation by counsel of the Indemnified Person or
Indemnified Party and the indemnifying party would be inappropriate due to
actual or potential differing interests between such Indemnified Person or
Indemnified Party and any other party represented by such counsel in such
proceeding.  The indemnifying party shall pay for only one separate legal
counsel for the Indemnified Persons or the Indemnified Parties, as applicable,
and such counsel shall be selected by the Investor, if the Investor is entitled
to indemnification hereunder, or the Company, if the Company is entitled to
indemnification hereunder, as applicable.  The Indemnified Party or Indemnified
Person shall cooperate fully with the indemnifying party in connection with any
negotiation or defense of any such action or Claim by the indemnifying party and
shall furnish to the indemnifying party all information reasonably available to
the Indemnified Party or Indemnified Person which relates to such action or
Claim.  The indemnifying party shall keep the Indemnified Party or Indemnified
Person fully appraised at all times as to the status of the defense or any
settlement negotiations with respect thereto.  No indemnifying party shall be
liable for any settlement of any action, claim or proceeding effected without
its written consent, provided, however, that the indemnifying party shall not
unreasonably withhold, delay or condition its consent. No indemnifying party
shall, without the consent of the Indemnified Party or Indemnified Person,
consent to entry of any judgment or enter into any settlement or other
compromise which does not include as an unconditional term thereof the giving by
the claimant or plaintiff to such Indemnified Party or Indemnified Person of a
release from all liability in respect to such Claim.  Following indemnification
as provided for hereunder, the indemnifying party shall be surrogated to all
rights of the Indemnified Party or Indemnified Person with respect to all third
parties, firms or corporations relating to the matter for which indemnification
has been made.  The failure to deliver written notice to the indemnifying party
within a reasonable time of the commencement of any such action shall not
relieve such indemnifying party of any liability to the Indemnified Person or
Indemnified Party under this Section 6, except to the extent that the
indemnifying party is prejudiced in its ability to defend such action.

(d)  The indemnity agreements contained herein shall be in addition to (i) any
cause of action or similar right of the Indemnified Party or Indemnified Person
against the indemnifying party or others, and (ii) any liabilities the
indemnifying party may be subject to pursuant to the law.

Section 7.  CONTRIBUTION.

To the extent any indemnification by an indemnifying party is prohibited or
limited by law, the indemnifying party agrees to make the maximum contribution
with respect to any amounts for which it would otherwise be liable under Section
6 to the fullest extent permitted by law; provided, however, that: (i) no
contribution shall be made under circumstances where the maker would not have
been liable for indemnification under the fault standards set forth in Section
6; (ii) no seller of Registrable Securities guilty of fraudulent
misrepresentation (within the meaning of Section 11(f) of the 1933 Act) shall be
entitled to contribution from any seller of Registrable Securities who was not
guilty of fraudulent misrepresentation; and (iii) contribution by any seller of
Registrable Securities shall be limited in amount to the net amount of proceeds
received by such seller from the sale of such Registrable Securities.

Section 8.      REPORTS UNDER THE 1934 ACT.

        With a view to making available to the Investor the benefits of Rule 144
        promulgated under the 1933 Act or any other similar rule or regulation
        of the SEC that may at any time permit the Investor to sell securities
        of the Company to the public without registration ("Rule 144"), the
        Company agrees to:

(a)     make and keep public information available, as those terms are
understood and  defined in Rule 144;

(b)     file with the SEC in a timely manner all reports and other documents
required of the Company under the 1933 Act and the 1934 Act so long as the
Company remains subject to such requirements (it being understood that nothing
herein shall limit the Company's obligations under Section 5(c) of the
Investment Agreement) and the filing of such reports and other documents is
required for the applicable provisions of Rule 144; and

(c)     furnish to the Investor, promptly upon request, (i) a written statement
by the Company that it has complied with the reporting requirements of Rule 144,
the 1933 Act and the 1934 Act, (ii) a copy of the most recent annual or
quarterly report of the Company and such other reports and documents so filed by
the Company, and (iii) such other information as may be reasonably requested to
permit the Investor to sell such securities pursuant to Rule 144 without
registration.

Section 9.  NO ASSIGNMENT OF REGISTRATION RIGHTS.

 The rights under this Agreement shall not be assignable.

Section 10.  AMENDMENT OF REGISTRATION RIGHTS.

Provisions of this Agreement may be amended only with the written consent of the
Company and Investor.

Section 11.  MISCELLANEOUS.

(a)  Any notices or other communications required or permitted to be given under
the terms of this Agreement that must be in writing will be deemed to have been
delivered (i) upon receipt, when delivered personally; (ii) upon receipt, when
sent by facsimile (provided a confirmation of transmission is mechanically or
electronically generated and kept on file by the sending party); or (iii) one
day after deposit with a nationally recognized overnight delivery service, in
each case properly addressed to the party to receive the same.  The addresses
and facsimile numbers for such communications shall be:

If to the Company:


Human Biosystems
1127 Harker Avenue
Palo Alto, California  94301
Telephone:        650-323-0943
Facsimile:      650-327-8658

If to the Investor:

Dutchess Private Equities Fund, II, LP
312 Stuart St, Third Floor
Boston, MA 02116
Telephone:      617-960-3570
Facsimile:      617-960-3772

Each party shall provide five business days prior notice to the other party of
any change in address, phone number or facsimile number.

(b)  Failure of any party to exercise any right or remedy under this Agreement
or otherwise, or delay by a party in exercising such right or remedy, shall not
operate as a waiver thereof.

(c)    The laws of the Commonwealth of Massachusetts shall govern all issues
arising from or related to this Agreement without regard to the principles of
conflict of laws. Each party hereby irrevocably submits to the exclusive
jurisdiction of the state and federal courts sitting in the City of Boston,
County of Suffolk, for the adjudication of any dispute hereunder or in
connection herewith or with any transaction contemplated hereby or discussed
herein, and hereby irrevocably waives, and agrees not to assert in any suit,
action or proceeding, any claim that it is not personally subject to the
jurisdiction of any such court, that such suit, action or proceeding is brought
in an inconvenient forum or that the venue of such suit, action or proceeding is
improper. Each party hereby irrevocably waives personal service of process and
consents to process being served in any such suit, action or proceeding by
mailing a copy thereof to such party at the address for such notices to it under
this Agreement and agrees that such service shall constitute good and sufficient
service of process and notice thereof. Nothing contained herein shall be deemed
to limit in any way any right to serve process in any manner permitted by law.
If any provision of this Agreement shall be invalid or unenforceable in any
jurisdiction, such invalidity or unenforceability shall not affect the validity
or enforceability of the remainder of this Agreement in that jurisdiction or the
validity or enforceability of any provision of this Agreement in any other
jurisdiction.

(d) This Agreement and the Transaction Documents constitute the entire agreement
among the parties hereto with respect to the subject matter hereof and thereof.
There are no restrictions, promises, warranties or undertakings, other than
those set forth or referred to herein and therein.

(e)  This Agreement and the Transaction Documents supersede all prior agreements
and understandings among the parties hereto with respect to the subject matter
hereof and thereof.

(f)  The headings in this Agreement are for convenience of reference only and
shall not limit or otherwise affect the meaning hereof.  Whenever required by
the context of this Agreement, the singular shall include the plural and
masculine shall include the feminine.  This Agreement shall not be construed as
if it had been prepared by one of the parties, but rather as if all the parties
had prepared the same.

(g)  This Agreement may be executed in two or more identical counterparts, each
of which shall be deemed an original but all of which shall constitute one and
the same agreement.  This Agreement, once executed by a party, may be delivered
to the other party hereto by facsimile transmission of a copy of this Agreement
bearing the signature of the party so delivering this Agreement.

(h)  Each party shall do and perform, or cause to be done and performed, all
such further acts and things, and shall execute and deliver all such other
agreements, certificates, instruments and documents, as the other party may
reasonably request in order to carry out the intent and accomplish the purposes
of this Agreement and the consummation of the transactions contemplated hereby.

* * *




SIGNATURE PAGE OF REGISTRATION RIGHTS AGREEMENT


Agreed as of the date first written above.

DUTCHESS PRIVATE EQUITIES FUND, II, L.P.,
BY ITS GENERAL PARTNER,
DUTCHESS CAPITAL MANAGEMENT, LLC


By:/s/ Douglas H. Leighton
 -----------------------------------------
       Douglas H. Leighton, Managing Member


HUMAN BIOSYSTEMS,

By:/s/ Harry Masuda
-------------------------------------------
       Harry Masuda, Chief Executive Officer